1. Field of the Invention
The present invention concerns an improved heat exchanger.
2. Related Art
In particular, the invention concerns a heat exchanger for exchanging heat between at least two fluids being guided through the heat exchanger, whereby the heat exchanger is of the type which is built of parallel plates which are connected by means of connecting walls to define chambers provided with an inlet and an outlet. An inlet or outlet is situated in the connecting walls.
Both fluids are sent through adjacent chambers which are separated from one another by means of an above-mentioned plate, such that the heat can be transferred from one fluid to another fluid via the above-mentioned plate, which is thereby made of a heat-conducting material such as copper or aluminium.
In order to promote the heat transfer, strips with cooling fins are provided in the chambers between the parallel plates, which are also made of a heat-conducting material and which must enhance the contact surface between a fluid flowing through and the heat-conducting material of the heat exchanger in the known manner.
Said cooling fins guide the flow over a certain length of the chambers in a particular, preferred direction, whereby the shape of the cooling fins forces the flow to make a zigzag movement along the above-mentioned preferred direction.
Depending on the available space for the heat exchanger and the location of supply and discharge of the fluids, the above-mentioned inlets and outlets may be provided in different locations.
A first possibility is to guide the fluid in a straight line through a chamber, whereby the inlet and the outlet are situated in the extension of the preferred direction of the cooling fins.
Another possibility is to locally change the flow direction of the fluid one or several times as it flows through a chamber, for example when, due to lack of space or for other reasons, an inlet or an outlet must be positioned laterally in relation to a direction of flow through the strips with cooling fins, and as a result, the flow direction of the fluid must hereby take a hooked bend at the inlet or at the outlet.
In order to guide said change in the flow direction, guiding profiles are used which in some known embodiments of heat exchangers are formed of strips with cooling fins which connect at right angles, whereby the strips are mitred at an angle of preferably 45° and are joined so as to bend away the flow at right angles.
The lateral inlet and/or outlet must be sufficiently wide so as to obtain a good guiding, whereby for example in the case of a mitre joint of 45°, the inlet or outlet is equally wide as the width of the heat exchanger measured in a direction transversal to the longitudinal direction of the actual cooling fins.
This implies that the length of such a heat exchanger will increase along with the width, resulting in a sizeable heat exchanger.
In other known embodiments, use is made of a specially provided guiding profile in the shape of a pleated, thin metal plate which is each time folded down at right angles along successive parallel folding lines so as to form a profile with a series of successive parallel ridges and grooves as if it were, defined by parallel standing walls formed of folded plate which are alternately connected at the top or at the bottom by folded strips of the metal plate and whereby, in the standing walls, passages are provided at regular distances from one another.
Said guiding profile extends over the entire width of the heat exchanger between two opposite walls of the heat exchanger and thereby connects with one far end to an inlet or outlet in an above-mentioned wall, whereas the guiding profile also connects at right angles to the strips with cooling fins with one side wall, such that the fluid flowing in the guiding profile in the longitudinal direction is diverted at right angles in the direction of the preferred direction of the cooling fins.
A disadvantage of such profiles, however, is that they are difficult to produce and are not firm either, as a result of which they are easily deformed while being transported or processed.
As a result, such guiding profiles have to be put back into shape before use by means of an additional rolling or pressing operation or any other operation to flatten the guiding profiles.
Such an additional operation is disadvantageous in that it makes the production costs rise and in that the guiding profile is weakened due to fine cracks which may possibly occur, which has a negative effect on the general strength of the heat exchanger.
Moreover, it appears that following the above-mentioned rolling or pressing operation, the height of the guiding profile still is not entirely equal everywhere, such that in certain places, the guiding profile makes a good contact with the parallel plates defining the chamber in which the guiding profile has been provided, whereas in other places there is no contact or only a partial one, which results in a weak point in these places given the freedom of movement of the plates there.